Facebook just bought tbh, an app teens are obsessed with that's at the top of the App Store — here's how it works

Tbh keeps everything anonymous except the person's gender.
Tbh
Anonymous polling app tbh has been at the top of the App Store's free apps chart for weeks — and Facebook took notice.

On Monday, Facebook announced it bought the 3-month-old app. Tbh will remain a standalone app, but its founders will move into Facebook's Silicon Valley headquarters.

Tbh, which is an acronym for "To be honest," bills itself as "the only anonymous app with positive vibes."

The app isn't a standard messaging app like Yik Yak or Sarahah, though: Instead, users are presented with a series of prompts about their friends like, "Should DJ every party" or "Hotter than the sun" and four options for friends that best fit that description.

The name of the app follows a similar trend among teens who use the phrase "tbh" on Instagram to say something nice about their friends. A tbh is used almost like a form of Instagram currency, since you can trade a tbh for a like on one of your photos. Whether or not the app's name was inspired by that, tbh bears a lot of similarities to the trend.

Tbh is designed for users 13 and up, and allows those who sign up to select their school and grade level. But you can still use tbh if you're in college or have already graduated.

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Next, you'll select your gender, which is the only thing about you that's shared with other users. One cool thing about tbh: There's an option for users who don't identify as either male or female.

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Tbh sets up the app like a game. You're presented with a series of polls — 12 at a time — then four options of friends to choose from. Tbh says your responses are entirely anonymous.

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The polls are generally pretty lighthearted. While not always 100% positive, the polls are never mean-spirited or cruel. You can submit your own polls to the app, but they have to be "uplifting" in nature.

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If you don't think any of the four friends you're presented with fit a description in a poll, you can hit the "shuffle" button — the app will present with you a few new friends to choose from. If you don't like a question or just don't want to vote, you can hit "skip."

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If someone chooses your name in a poll, you'll get a notification in your inbox. You'll be able to see the gender of the person who voted for you, but that's all.

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The more times someone picks you in a poll, the more gemstones you get (they'll be pink if a girl picks you and blue if a boy picks you). Tbh says the gems will let you unlock more questions and future features.

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Tbh was only available in Florida, Washington, Texas, California, Connecticut, Massachusetts, Rhode Island, Georgia, and Indiana to start, but is now available in 37 states. The app isn't available for Android yet, but it's free to download from the App Store.

Despite launching this past August, the app has now been downloaded by more than 5 million people, and users have sent more than a billion messages.